The annual consumption of polymer materials has climbed to more than 260 million tons, and half of this is synthesized by radical polymerization. Radical polymerization is widely used to synthesize polymers through the polymerization of unsaturated bond-bearing small molecules (monomers), e.g., styrene, ethylene, vinyl chloride, vinyl acetate, methyl methacrylate, acrylonitrile, acrylic acid, acrylamide, vinylpyrrolidone, and tetrafluoroethylene. Radical polymerization is a chain reaction formed mainly of the following three steps: initiation, growth, and termination. The radicals generated when the initiator is cleaved by, e.g., heat or light, attack the unsaturated bond-bearing monomer. The resulting monomer radical sequentially attacks additional monomer, resulting in growth of the polymer chain, and termination ultimately occurs through the recombination or disproportionation of radicals with each other or through chain transfer by a radical.